- Phylum Echinoderms (Invertebrates)
- Phylum Chordata (mostly Vertebrates)
- Deuterostome = Developmental similarities
- radial cleavage of embryo
- anus forms first
- HOWEVER: other animal phyla share some of these traits
- Deuterostomes now defined by DNA
Groups differ in how the digestive system developes
Add lungs/lung derivatives to phylogeny
6,000 species
Amniotic egg contains 4 membranes around embryo. Surrounds embryo with amniotic fluid